1. Field of the Invention
This invention relates to a structure of an Al/Ti layered interconnection heavily used as an interconnection or the like for a semiconductor device and a method of forming the same.
2. Description of the Related Art
An Al/Ti stacked or layered interconnection has been known as an interconnection for providing excellent resistance to electromigration (EM). Since Al formed over Ti (normally oriented to a (0002) surface or plane) is firmly oriented onto a (111) plane and an interconnection in which a small amount of Ti has entered an Al layer, is enhanced, the EM resistance has been considered to improve. It is however known that when a structure formed by simply stacking a Ti layer and an Al layer on each other is used, both layers undergo a chemical reaction at an interface between the layers by a heat treatment (corresponding to heat treatment often used during a manufacturing process of a semiconductor device) at a temperature of 400.degree. C. or above thereby to increase wiring resistances. This has been disclosed in, for example, a reference I: Appl. Phys. Lett., vol. 23, No. 2, 15, p.99 (1973) and a reference II: J. Appl. Phys., 69(7), p.3907 (1991). Therefore, an Al layer containing Si has been used as the Al layer in the Al/Ti layered interconnection. This is because the reaction between Ti and Al can be retarded owing to the containing of Si in the Al layer. This has been described in, for example, a reference III proposed by inventors of this application, "Extended Abstracts of the 1994 International Conference on Solid State Devices and Materials, Yokohama), 1994, pp.952-954.